Enhancing data processing performance by cache management of fingerprint index

ABSTRACT

Various embodiments for improving hash index key lookup caching performance in a computing environment are provided. In one embodiment, for a cached fingerprint map having a plurality of entries corresponding to a plurality of data fingerprints, reference count information is used to determine a length of time to retain the plurality of entries in cache. Those of the plurality of entries having a higher reference counts are retained longer than those having lower reference counts.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.13/801,472, filed on Mar. 13, 2013, which is a Continuation of U.S.patent application Ser. No. 13/465,456, filed on May 7, 2012.

FIELD OF THE INVENTION

The present invention relates in general to computers, and moreparticularly to a method, system, and computer program product forenhancing data processing performance in computing storage environments.

DESCRIPTION OF THE RELATED ART

Computers and computer systems are found in a variety of settings intoday's society. Computing environments and networks may be found athome, at work, at school, in government, and in other settings.Computing environments increasingly store data in one or more storageenvironments, which in many cases are remote from the local interfacepresented to a user.

These computing storage environments may use many storage devices suchas disk drives, often working in concert, to store, retrieve, and updatea large body of data, which may then be provided to a host computerrequesting or sending the data. In some cases, a number of data storagesubsystems are collectively managed as a single data storage system.These subsystems may be managed by host “sysplex” (system complex)configurations that combine several processing units or clusters ofprocessing units. In this way, multi-tiered/multi-system computingenvironments, often including a variety of types of storage devices, maybe used to organize and process large quantities of data.

SUMMARY OF THE INVENTION

Many multi-tiered/multi-system computing environments implement datadeduplication technologies to improve storage performance by reducingthe amount of duplicated storage across storage devices. Datadeduplication systems are increasingly utilized because they help reducethe total amount of physical storage that is required to store data.This reduction is accomplished by ensuring that duplicate data is notstored multiple times. Instead, for example, if a chunk of data matcheswith an already stored chunk of data, a pointer to the original data isstored in the virtual storage map instead of allocating new physicalstorage space for the new chunk of data. Thus each chunk of data in adata deduplication system is associated with a “reference counter” thatindicates how many virtual map elements are pointing to a given chunk ofdata.

Such data deduplication systems must grapple with the problem of beingable to store large amounts of mapping information that map virtualstorage space to physical disk storage space, for example, or so-called“fingerprints” of data chunks that map to already stored blocks of data.This situation is at least partly due to the fact that unliketraditional Redundant Array of Independent Disks (RAID) systems wherevirtual-to-physical mappings are determined algorithmically, datadeduplication maps may point to any random chunk of physical diskstorage. When inline data deduplication is used, it is generallyimpractical or impossible to store the complete map in memory because ofits size. Accordingly, only portions of the map are cached depending onaccess pattern. As a result, the correct caching and retrieval of themost relevant parts of these storage maps at a particular time becomeincreasingly important.

Inline data deduplication systems must maintain the aforementionedstorage mapping information (including reference counter information)in-memory for fast access to data. Otherwise, an additional map faultpenalty is incurred when fetching mapping information from physicalstorage, which thereby significantly increases storage latency. Hence,the storage controller must be able to identify those parts of thededuplication map that must be cached in-memory at a particular time. Incontrast, conventional caching algorithms are based on traditional“locality of reference” models to cache virtualization maps. A needexists for a more effective way of cache management for such storagemaps, and in particular for purposes of the present invention, thefingerprint index, or map.

In view of the forgoing need to better manage the caching of suchfingerprint mapping information, various embodiments for improving hashindex key lookup caching performance in a computing environment by aprocessor are provided. In one embodiment, by way of example only, for acached fingerprint map having a plurality of entries corresponding to aplurality of data fingerprints, reference count information is used todetermine the length of time to retain the plurality of entries incache. Those of the plurality of entries having a higher referencecounts are retained longer than those having lower reference counts.

In one embodiment, by way of example only, for a cached fingerprint maphaving a plurality of entries corresponding to a plurality of datafingerprints, reference count information obtained from a datadeduplication engine is used to determine a length of time to retain theplurality of entries of the fingerprint map in cache, by: 1) examiningthe reference count information of the plurality of entries of thefingerprint map in the cache and a storage policy related to theplurality of entries to establish a retention duration for the pluralityof entries, and 2) querying whether the reference count information fora data segment has been incremented, the incremented reference countinformation indicating a frequency of times the data segment has beenaccessed, or whether a predetermined time interval has expired. If thereference count information for a data segment has not been incrementedor if the predetermined time interval has not expired, reiterating thestep of querying. If the reference count information for a data segmenthas been incremented or if the predetermined time interval has expiredin which no physical activity has been observed on a physical block,re-determining a new appropriate duration of retention in the cache.

In addition to the foregoing exemplary embodiment, various additionalembodiments are provided and supply related advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the invention will be readilyunderstood, a more particular description of the invention brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered to be limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating an exemplary computingenvironment which may implement aspects of the present invention;

FIG. 2 is a block diagram showing a hardware structure of a data storagesystem, again in which aspects of the present invention may beimplemented;

FIG. 3A is a block diagram of a cache system embodiment of the presentinvention illustrating a relationship between data deduplication system,data frequency index map and cache management module for improvingcaching performance;

FIG. 3B is a block diagram of a cache system embodiment of the presentinvention illustrating a relationship between cache management moduleand fingerprint cache for improving caching performance;

FIG. 4 is a flow chart diagram of an exemplary embodiment for enhancingdata caching performance in which aspects of the present invention maybe implemented;

FIG. 5 is a flow chart diagram of an additional exemplary embodiment forenhancing data caching performance, again in which aspects of thepresent invention may be implemented; and

FIG. 6 is a flow chart diagram of an exemplary embodiment for cachemanagement of data segments, again in which aspects of the presentinvention may be implemented.

DETAILED DESCRIPTION OF THE DRAWINGS

As one of ordinary skill in the art will appreciate, as computingstorage environments grow, so does the limitation on the ability for anywhole storage mapping of associated data segments to be cached in memoryfor quick access. This limitation becomes more pronounced when inlinedata deduplication systems are implemented, as again as previouslydescribed, it is difficult or impossible to store a complete storagemapping in cache memory due to its size. As a result, only portions ofthe storage mapping are cached at any particular time.

To address and improve upon the current state of the art, theillustrated embodiments describe mechanisms to utilize so-called“reference count” information of various data segments as provided bythe deduplication system (e.g., deduplication engine) to enhance afingerprint map caching algorithm to better identify parts of thefingerprint storage mapping information that must be cached in-memory toensure faster inline data access, and thereby, improve the cachingperformance of the storage environment.

Storage systems that incorporate data deduplication functionalityimplement a reference count for each segment of data, which indicates,for example, how many segments of virtual storage map onto a singlesegment of physical storage. Reference count information is generallyreadily available, as such reference count functionality is found inmost, if not all, inline data deduplication systems. By improvingcaching performance of fingerprint storage mapping information, theaverage latency of input/output (I/O) operations in inline datadeduplication systems may be significantly reduced.

In the following description, reference is made to the accompanyingdrawings which form a part hereof and which illustrate severalembodiments of the present invention. It is understood that otherembodiments may be utilized and structural and operational changes maybe made without departing from the scope of the present invention.

Turning to FIG. 1, an example computer system 10 is depicted in whichaspects of the present invention may be realized. Computer system 10includes central processing unit (CPU) 12, which is connected to massstorage device(s) 14 and memory device 16. Mass storage devices mayinclude hard disk drive (HDD) devices, which may be configured in aredundant array of independent disks (RAID). The cache managementoperations further described may be executed on device(s) 14, located insystem 10 or elsewhere. Memory device 16 may include such memory aselectrically erasable programmable read only memory (EEPROM) or a hostof related devices. Memory device 16 and mass storage device 14 areconnected to CPU 12 via a signal-bearing medium. In addition, CPU 12 isconnected through communication port 18 to a communication network 20,having an attached plurality of additional computer systems 22 and 24.The computer system 10 may include one or more processor devices (e.g.,CPU 12) and additional memory devices 16 for each individual componentof the computer system 10 to execute and perform each operationdescribed herein to accomplish the purposes of the present invention.

FIG. 2 is an exemplary block diagram 200 showing a hardware structure ofa data storage system in a computer system according to the presentinvention. Host computers 210, 220, 225, are shown, each acting as acentral processing unit for performing data processing as part of a datastorage system 200. The hosts (physical or virtual devices), 210, 220,and 225 may be one or more new physical devices or logical devices toaccomplish the purposes of the present invention in the data storagesystem 200. In one embodiment, by way of example only, a data storagesystem 200 may be implemented as IBM® System Storage™ DS8000™. A Networkconnection 260 may be a fibre channel fabric, a fibre channel point topoint link, a fibre channel over ethernet fabric or point to point link,a FICON or ESCON I/O interface, any other I/O interface type, a wirelessnetwork, a wired network, a LAN, a WAN, heterogeneous, homogeneous,public (i.e. the Internet), private, or any combination thereof. Thehosts, 210, 220, and 225 may be local or distributed among one or morelocations and may be equipped with any type of fabric (or fabricchannel) (not shown in FIG. 2) or network adapter 260 to the storagecontroller 240, such as Fibre channel, FICON, ESCON, Ethernet, fiberoptic, wireless, or coaxial adapters. Data storage system 200 isaccordingly equipped with a suitable fabric (not shown in FIG. 2) ornetwork adapter 260 to communicate. Data storage system 200 is depictedin FIG. 2 comprising storage controller 240 and storage 230.

To facilitate a clearer understanding of the methods described herein,storage controller 240 is shown in FIG. 2 as a single processing unit,including a microprocessor 242, system memory 243 and nonvolatilestorage (“NVS”) 216, which will be described in more detail below. It isnoted that in some embodiments, storage controller 240 is comprised ofmultiple processing units, each with their own processor complex andsystem memory, and interconnected by a dedicated network within datastorage system 200. Storage 230 may be comprised of one or more storagedevices, such as storage arrays, which are connected to storagecontroller 240 by a storage network.

In some embodiments, the devices included in storage 230 may beconnected in a loop architecture. Storage controller 240 manages storage230 and facilitates the processing of write and read requests intendedfor storage 230. The system memory 243 of storage controller 240 storesprogram instructions and data that the processor 242 may access forexecuting functions associated with managing storage 230. In oneembodiment, system memory 243 includes, is associated, or is incommunication with the operation software 250, and configured in partfor accomplishing functionality of the present invention. As shown inFIG. 2, system memory 243 may also include or be in communication with adata cache 245 for storage 230, also referred to herein as a “cachememory”, for buffering “write data” and “read data”, which respectivelyrefer to write/read requests and their associated data. In oneembodiment, data cache 245 is allocated in a device external to systemmemory 243, yet remains accessible by microprocessor 242 and may serveto provide additional security against data loss, in addition tocarrying out the operations as described in herein.

In some embodiments, data cache 245 is implemented with a volatilememory and non-volatile memory and coupled to microprocessor 242 via alocal bus (not shown in FIG. 2) for enhanced performance of data storagesystem 200. The NVS 216 included in data storage controller isaccessible by microprocessor 242 and serves to provide additionalsupport for operations and execution of the present invention asdescribed in other figures. The NVS 216, may also referred to as a“persistent” cache, or “cache memory” and is implemented withnonvolatile memory that may or may not utilize external power to retaindata stored therein. The NVS may be stored in and with the data cache245 for any purposes suited to accomplish the objectives of the presentinvention. In some embodiments, a backup power source (not shown in FIG.2), such as a battery, supplies NVS 216 with sufficient power to retainthe data stored therein in case of power loss to data storage system200. In certain embodiments, the capacity of NVS 216 is less than orequal to the total capacity of data cache 245.

Storage 230 may be physically comprised of one or more storage devices,such as storage arrays. A storage array is a logical grouping ofindividual storage devices, such as a hard disk. In certain embodiments,storage 230 is comprised of a JBOD (Just a Bunch of Disks) array or aRAID (Redundant Array of Independent Disks) array. A collection ofphysical storage arrays may be further combined to form a rank, whichdissociates the physical storage from the logical configuration. Thestorage space in a rank may be allocated into logical volumes, whichdefine the storage location specified in a write/read request.

In one embodiment the storage system as shown in FIG. 2 may include alogical volume, or simply “volume,” with corresponding varying kinds ofallocations. Storage 230 a, 230 b and 230 n are shown as ranks in datastorage system 200, and are referred to herein as rank 230 a, 230 b and230 n. Ranks may be local to data storage system 200, or may be locatedat a physically remote location. In other words, a local storagecontroller may connect with a remote storage controller and managestorage at the remote location. Rank 230 a is shown configured with twoentire volumes, 234 and 236, as well as one partial volume 232 a. Rank230 b is shown with another partial volume 232 b. Thus volume 232 isallocated across ranks 230 a and 230 b. Rank 230 n is shown as beingfully allocated to volume 238—that is, rank 230 n refers to the entirephysical storage for volume 238. From the above examples, it will beappreciated that a rank may be configured to include one or more partialand/or entire volumes. Volumes and ranks may further be divided intoso-called “tracks,” which represent a fixed block of storage. A track istherefore associated with a given volume and may be given a given rank.

The storage controller 240 may include a data deduplication engine 255,cache management module 257, block map 259, fingerprint map 261, andfingerprint cache 263 as will be further described. The cache managementmodule 257 may work in conjunction with each and every component of thestorage controller 240, the hosts 210, 220, 225, and storage devices230. The cache management module 257 may be, as one of ordinary skill inthe art will appreciate, structurally one complete module or may beassociated and/or included with other individual modules. The cachemanagement module 257 may also be located in the data cache 245 or othercomponents.

The storage controller 240 includes a control switch 241 for controllingthe fiber channel protocol to the host computers 210, 220, 225, amicroprocessor 242 for controlling all the storage controller 240, anonvolatile control memory 243 for storing a microprogram (operationsoftware) 250 for controlling the operation of storage controller 240,data for control and each table described later, data cache 245 fortemporarily storing (buffering) data, and buffers 244 for assisting thedata cache 245 to read and write data, a control switch 241 forcontrolling a protocol to control data transfer to or from the storagedevices 230. Multiple buffers 244 may be implemented with the presentinvention to assist with the operations as described herein.

The storage controller 240 is shown including a data deduplicationengine 255, storage map/data frequency index map (DFIM) 259 (“storagemap” 259), and cache management module 257. The data deduplicationengine 255, cache management module 257 and DFIM 259 may operate inconjunction with each and every component of the storage controller 240,the hosts, 210, 220, 225, and storage devices 230, to accomplishfunctionality according to the present invention. The data deduplicationengine 255, cache management module 257 and DFIM 259 may be structurallyone complete module or may be associated and/or incorporated withinother individual modules. The cache management module 257 and DFIM 259may also be incorporated in the cache 245 or other components.

Data deduplication engine 255 is configured for performing, inconjunction with other components of storage controller 240 such asmicroprocessor 242, data deduplication operations on write data passedthrough storage controller 240 to storage 230.

As previously indicated, storage controller 240 includes a datafrequency block map 259 for short. Data cache 245 (or what may be termedholistically as cache system 245 (which may incorporate cache managementmodule 257, block map 259, or even data deduplication engine 255)accepts write data from hosts 210, 220, and 225, or similar devices,that is then placed in cache memory 245. Data deduplication engine 255then tests the write data for duplication in the cache memory 245 andwrites an index and frequency for such in the block map 259. Inconjunction with block map 259, the data deduplication engine generatesfingerprint information corresponding to stored blocks of data, writingan index for such in the fingerprint map 261. Fingerprints of new blocksof data are then compared with the indexed fingerprints in thefingerprint map to determine if exact replicas of data are found.

Fingerprint map 261 may be partially or wholly temporarily stored infingerprint cache 263. In one embodiment, the size of fingerprint map261 is such (due to the immense underlying storage 230 and dataprocessing occurring in relation to such storage 230) that only aportion of the fingerprint map 261 may be stored “in-memory” (cached) inthe fingerprint cache 263 at any one time.

Turning now to FIG. 3A, a block diagram of various functional aspects300 of the present invention are depicted as an exemplary flow,specifically the creation of reference count information to be laterused in cache management by the cache management module 260.Specifically, data cache system 245 is shown to accept write data 302 tobe processed through data deduplication engine 255 as a write operation304 to data cache 245. As the write data 302 is processed through thedata deduplication engine 255, and as previously described, the writedata 302 is tested for duplication with existing storage, and thededuplication engine 255 passes the frequency and index information 306to the data frequency index/block map 259. Storage systems thatincorporate data deduplication functionality as shown in FIG. 3, includea reference count for each chunk of data, which indicates how manychunks of virtual storage map onto a single chunk of physical storage,among other indications.

As data is read 312 out of the cache 245, the block map 259 is updated.The information contained in block map 259 is provided, includingreference count information 310, to the cache management module 260,which is also in bi-directional communication 314 between the data cache245 and the storage controller 240 (FIG. 2), and thereby hosts 210, 220,and 225 as read data 312.

Turning now to FIG. 3B, a block diagram of various function aspects 320of the present invention are depicted as an additional exemplary flow,specifically the use of reference count information 310 as previouslydescribed to perform cache management information to the fingerprint map261. Based at least in part on the activities previously described inFIG. 3A, the cache management module 260 may determine which of portionsof the fingerprint map 261 to be placed in the fingerprint cache 263 andfor what appropriate length of time as will be further illustrated,according to aspects of the present invention.

As previously described, reference count information 310 is used by thecache management module 260 to determine which portions of thefingerprint map 261 will be retained in the fingerprint cache 263. Awrite command may be processed by the data deduplication engine 255(e.g., FIG. 3A) to obtain/generate a fingerprint representative of thewrite data to be written to storage. The fingerprint information 322 isthen provided to the cache management module 260 as shown, which callsup the cached portion of the fingerprint map 261 from the fingerprintcache 263 (via bilateral communication 316) to determine if an exactmatch is found. This result is provided as fingerprint data 318 to thedata deduplication engine 255. If an exact match is found, the referencecount for such data may be updated, but the data is not rewritten tophysical storage. In one embodiment, based at least in part on use ofthe reference count information to determine which portions of thefingerprint map are cached in-memory, the likelihood of the relevantportion of the fingerprint map 261 corresponding to the incomingfingerprint information 322 is increased, and alleviates a further needto call up additional portions of the fingerprint map 261 from storageaccording to mechanisms further described.

Turning now to FIG. 4, a flow chart diagram of a method for improvingcaching performance in a storage environment is shown in one exemplaryembodiment. Method 400 begins (step 402) by using the aforementionedreference count information to determine an appropriate length of timeto retain particular entries (e.g., portions) of the aforementionedfingerprint map 261 (e.g., FIG. 3B) in the fingerprint cache 263 (step404). The method 400 ends (step 406).

FIG. 5, following, is a flow chart diagram of a method for implementingsuch utilization of reference count information, as shown previously inFIG. 4, in a further exemplary embodiment. Here, method 500 begins (step502) by examining reference count data obtained from the deduplicationengine in the course of a deduplication operation as previouslydescribed (step 504). Based on the reference count information (and/orby implementation of a particular storage policy), a retention durationfor a particular entry in the fingerprint map, or for a number ofentries in the fingerprint map, is established (step 506).

Continuing with FIG. 5, the method 500 then queries if the referencecount information for the referenced data segment has been updated(e.g., incremented pursuant to a deduplication operation), or whether,for example, a predetermined time interval has expired (step 508) inwhich no activity is observed on the physical block. If this is thecase, the retention duration that was previously established in step 506is revisited to re-determine a new appropriate duration of retention inthe cache (step 510). Returning to step 508, if the reference countinformation is not updated, or the predetermined time interval is notexpired, the method 500 returns to step 508 with the passage of time toagain query whether either or both of these conditions has beensatisfied.

The methodologies described in FIGS. 4 and 5, previously may incorporatecertain weighting factors into consideration, such as a predeterminedweight that diminishes over time such that even data segments havinghigh reference counts that see little or no activity will see theirassociated weights (and thereby the importance of the fingerprintinformation for the referenced data segment to be retained in the cache)slowly decreased. As one of ordinary skill in the art will appreciate,these weighting factors may be utilized in various ways with or withoutother considerations so as to effectively address the relativeimportance of fingerprint information of referenced data segments overthe passage of time, use, resource utilization (such as bandwidth andother scarce system resources), and the like in order to suit aparticular application.

As one of ordinary skill in the art will appreciate, a wide variety ofstorage policies (which may, for example, be established with theassistance of a administrator/user) may be brought to bear on whether aparticular entry or set of entries (i.e., portions) in the fingerprintmap should be retained for a certain duration, based on the currentreference count information for that entry or set of entries. Sincereference count information indicates, for a given segment of data, thelikelihood of a particular entry being accessed, this same informationmay be intelligently used by such policies or otherwise in map cachingmechanisms (such as a map caching algorithm that may be implemented bythe cache management module previously described) in order to determinethose candidate entries stored in the fingerprint map that should bepaged out from cache memory.

In view of the foregoing, consider the following example. Ten (10)mapping table entries are established as candidates for being paged out.Of those ten mapping table entries, those that contain higher referencecounts (for all data segments together, in one embodiment) will be pagedout later than those that have a lower reference count. In this manner,fingerprint map portions having corresponding higher reference countsare retained longer, with the expectation that they will be reusedagain, and when this occurs, the particular entry will be found in cachefor fast access.

FIG. 6, following, illustrates a flow chart diagram of an exemplarymethod for retention of mapping table entries in cache using referencecount values, in which aspects of the present invention may beimplemented. Method 600 begins (step 602) with a query as to whether thecache is full, and whether despite this fact new map entries are to befetched from disk (thereby requiring other map entries to be paged out)(step 604). If this is the case, the fingerprint map entries arecollectively examined to determine which of those entries to page outfrom cache (step 606). As part of this examination process, method 600then queries if a particular examined entry has a reference count valuethat is high (for example, in one embodiment, above a particularthreshold set by policy) (step 608). If this is the case, the entry isretained in cache (step 610). If the entry is determined not to have ahigh value, the entry is designated to be paged out from cache (step612) and a new map entry may be paged into cache in its place.

As will be appreciated by one of ordinary skill in the art, aspects ofthe present invention may be embodied as a system, method or computerprogram product. Accordingly, aspects of the present invention may takethe form of an entirely hardware embodiment, an entirely softwareembodiment (including firmware, resident software, micro-code, etc.) oran embodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module,” “process” or“system.” Furthermore, aspects of the present invention may take theform of a computer program product embodied in one or more computerreadable medium(s) having computer readable program code embodiedthereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wired, optical fiber cable, RF, etc., or any suitable combination of theforegoing. Computer program code for carrying out operations for aspectsof the present invention may be written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Java, Smalltalk, C++ or the like and conventionalprocedural programming languages, such as the “C” programming languageor similar programming languages. The program code may execute entirelyon the user's computer, partly on the user's computer, or entirely onthe remote computer or server. In the last scenario, the remote computermay be connected to the user's computer through any type of network,including a local area network (LAN) or a wide area network (WAN), orthe connection may be made to an external computer (for example, throughthe Internet using an Internet Service Provider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks. The computer program instructions may also beloaded onto a computer, other programmable data processing apparatus, orother devices to cause a series of operational steps to be performed onthe computer, other programmable apparatus or other devices to produce acomputer implemented process such that the instructions which execute onthe computer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the above figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

While one or more embodiments of the present invention have beenillustrated in detail, one of ordinary skill in the art will appreciatethat modifications and adaptations to those embodiments may be madewithout departing from the scope of the present invention as set forthin the following claims.

What is claimed is:
 1. A method for improving hash index key lookupcaching performance in a computing environment by a processor,comprising: for a cached fingerprint map having a plurality of entriescorresponding to a plurality of data fingerprints used by a datadeduplication system, using reference count information obtained from adata deduplication engine to determine a length of time to retain theplurality of entries of the fingerprint map in cache, by: examining thereference count information of the plurality of entries of thefingerprint map in the cache and a storage policy related to theplurality of entries to establish a retention duration for the pluralityof entries, and querying whether the reference count information for adata segment has been incremented, the incremented reference countinformation indicating a frequency of times the data segment has beenaccessed, or whether a predetermined time interval has expired; if thereference count information for a data segment has not been incrementedor if the predetermined time interval has not expired, reiterating thestep of querying; and if the reference count information for a datasegment has been incremented or if the predetermined time interval hasexpired in which no physical activity has been observed on a physicalblock, re-determining a new appropriate duration of retention in thecache.
 2. The method of claim 1, further including obtaining thereference count information from a data deduplication engine.
 3. Themethod of claim 1, further including, when the cache is full, retainingin the cache the plurality of entries of the fingerprint map havinghigher reference counts and removing from the cache the plurality ofentries of the fingerprint map having lower reference counts.
 4. Themethod of claim 1, further including performing the re-determining forevery reference count increment.
 5. The method of claim 1, whereindetermining the length of time to retain the plurality of entries incache includes implementing at least one policy corresponding to one ofthe length of time or at least one of the plurality of entries.
 6. Themethod of claim 1, wherein the determining the length of time to retainthe plurality of entries in cache is performed in approximatesynchronization with a deduplication operation for those of theplurality of entries retained in the cache.
 7. The method of claim 1,further comprising assigning a predetermined weight to the data segmentthat diminishes over time as physical activity observed on a physicalblock decreases.